Valentinka_1,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
</head>
<body>
<table>
<td><select name="oplata">
<option data-pb="1.01" data-opt="0"> 1</option>
<option data-pb="1" data-opt="0.75">2</option>
<option data-pb="1" data-opt="0">3</option>
</select></td>
</table>
<input type="button" value="go">
<script>
var plat_pb;
var plat_opt;
$('input').click(updatePlat)
function updatePlat()
{
var selected = $('[name=oplata] option:selected');
plat_pb = selected.data('pb');
plat_opt = selected.data('opt');
alert([plat_pb,plat_opt])
}
</script>
</body>
</html>